The Temporomandibular Joint (TMJ)

The TMJ is formed by the insertion of the mandibular condyle into the temporal bone and other anatomical structures in between, like the articular disc and ligaments in charge of the hinge and slide motion of the jaw. Additionally, the group of muscles in charge of mastication are also part of the TMJ complex and therefore, alterations in their anatomy, range of motion, tone and strength are going to have an impact on the joint.

Thus, two subgroups of disorders will determine the diagnosis and hence the treatment plan when any alteration appears in or around the TMJ. It is important to determine whether the pain is coming merely from the muscles (myofascial pain) or from the intra-articular structures of the joint itself (articular disc and ligaments).

• Muscular or myofascial disorders: these are the most common causes of TMJ dysfunction. The most common symptom is muscular pain as a result from cumulative pathological tension, fatigue or spasms of the masticatory muscles.
• Intra-articular disorders: refers to the disruption of the joint functions due to inflammation or mechanic disorders. According to the structures involved, these disorders can be painful or not.

Causes of TMJ dysfunctions

It is difficult to determine the exact cause of TMJ dysfunctions. This is due to the number of aspects that can influence the correct functioning of the masticatory system, including genetics, anatomical, physiological and psychological factors. A combination of these is usually what causes pain and dysfunction of the TMJ.

Disorders of the masticatory muscles are often the result of excessive tension, fatigue or spasms caused by pathological behaviours such as bruxism, teeth clenching and grinding, or adopting an abnormal posture.

Muscular painful disorders:

The most common cause for muscular pain and spasm is unconscious teeth clenching or bruxism, both are associated with psychiatric and psychological disturbances like stress, depression and anxiety. Thus, heavy bruxers might develop severe TMJ pain due to the hyperactivity of their masticatory muscles that results in severely increased muscular tone and tension. Other causes for muscular painful issues are autoimmune pathologies, fibromyalgia and other chronic pain conditions related to the back and neck.

On the other hand, causes of intra-articular pain include:

• Derangement of the internal joint: the intraarticular disc wears off and produces trauma between the jaw and skull bones.
• Displacement of the articular disc: the disc does not move along with the condyle during the jaw movements causing a clicking sound or pain.
• Osteoarthritis.
• Inflammation of the ligament involving the joint (capsular ligament).
• Hypermobility.
• Traumatic injuries.
• Inflammatory conditions like rheumatoid arthritis.

Symptoms

Typically, patients describe pain within the TMJ or mandible as the main symptom. Signs and symptoms of TMJ disorders may include:

• Pain or tenderness of your jaw or face.
• Pain in one or both of the temporomandibular joints.
• Aching pain in and around your ear.
• Headaches, otalgia, vertigo and hearing impairment.
• Difficulty chewing or pain while chewing.
• Locking of the joint, making it difficult to open or close your mouth.

TMJ disorders can also cause a clicking, popping or crepitus sound or grating sensation when you open your mouth or chew. But if there’s no pain or limitation of movement associated with your jaw clicking, you probably don’t need treatment for a TMJ disorder.

Diagnosis

As every other dental and orofacial diagnosis, to diagnose a TMJ disorder takes a full oral and facial examination. After following the patient’s history, a physical examination is conducted paying particular attention to the site, onset, character of the pain (what triggers, soothes or exacerbates it), radiation (to scalp or neck), duration and associated symptoms. The dentist will also look at your joint health, looking for ranges of motion of the mandible, pain during opening or closure, abnormal movements, tenderness or signs of bruxism.

If your dentist suspects a problem, you may need:

• Dental X-rays to examine your teeth and jaw.
• CT scan to provide detailed images of the bones involved in the joint.
• MRI to reveal problems with the joint’s disk or surrounding soft tissue.
• TMJ arthroscopy is sometimes used in the diagnosis of a TMJ disorder. During TMJ arthroscopy, your doctor inserts a small thin tube (cannula) into the joint space, and a small camera (arthroscope) is then inserted to view the area and to help determine a diagnosis.

Management

The majority of patients can be managed with a conservative approach. Almost 40% of symptomatic patients report spontaneous resolution of their symptoms and do not require treatment. This is particularly seen in patients whose symptoms are related to stressful life periods. In addition, more than half of the patients with a TMJ dysfunction diagnosis respond well to conservative measures.

Non-Pharmacological Treatment

• Raising and reassuring awareness: these can include referrals to psychotherapy (stress and anxiety management) physiotherapists and pain management specialists.
• Lifestyle changes: softer diet, rest (sleep hygiene, stress reduction).
• Warm compress over the affected region.
• Stretching and jaw exercises
• Splints: there have been benefits reported with the use of custom-made splints for patients with severe bruxism. These splints also help in preventing secondary effects such as severe dental abrasion and joint dysfunction.

Pharmacological Treatment

• NSAIDs: Unless contraindicated, the use of anti-inflammatory medications help relieve the pain associated with TMJ during the acute phase (no more than three days after the beginning of the painful episode).
• Muscle relaxants: are useful to release chronic spasms, especially in bruxers.
• Medications like tramadol or topical gels of diclofenac (voltaren) have shown little to no effect on TMJ pain management.

Referral to a maxillofacial surgeon should be considered in patients unresponsive to conservative treatment, patients with severe pain and/or dysfunction of the TMJ, and patients with a history of trauma or fracture of the TMJ complex. Furthermore, patients with persistent or worsening pain, or those with other red flag symptoms with no identifiable source, should be referred to specialist care for further investigation.

References

• Lomas, J., Gurenci, T., Jackson, C., Campbell, D. (2018). Temporomandibular dysfunction. Australian Journal of General Practice. 47 (4) 212-215. doi: 10.31128/AFP-10-17-4375
• Mayo clinic (2018). TMJ disorders. Retrieved from: https://www.mayoclinic.org/diseases-conditions/tmj/symptoms-causes/syc-20350941
  23/04/2020